STEREOTACTICAL INSTRUMENT

Abstract: Stereotactical instrument for identifying, by means of image sectional planes, the spatial position of an area (13) in a patient's body which is to be subjected to treatment, preferably radiation treatment, the position of the area being previously determined, for example by means of angiogram, PET, DSA, CT, MRI or X-ray equipment. The instrument comprises a non-yielding and radiolucent frame (2) which is arranged to support the patient's body and to support an indicating device (1, 2), a radiolucent fixing means (3) which is arranged inside the frame (2) and on which the patient's body is intended to rest, said fixing means (3) comprising a flexible casing which contains a yieldable substance, at a first stage the fixing means being adapted to permit that the patient is oriented in a desired position, partly sunk into the fixing means, and at a second stage the yieldable substance of the fixing means being given a non-yielding state, thereby fixing the patient in the desired position, and a partially non-radiolucent orienting means (8) which is mounted on at least one longitudinal side of the frame (2) and which is adapted to indicate the position of the respective image sectional plane through said area (13) in the patient's body.

Description: STEREOTACTICAL INSTRUMENT The present invention relates to a stereotactical instrument for identifying, by means of image sectional planes or markers, the spatial position of an area in a patient's body which is to be subjected to treatment, preferably radiation treatment, the position of the area being previously determined, for example by means of an- giogram, PET, DSA, CT, MRI or X-ray equipment, the in¬ strument comprising a non-yielding and radiolucent frame which is arranged to support the patient's body and to support an indicating device, a radiolucent fixing means which is arranged inside the frame and on which the pa¬ tient's body is intended to rest, said fixing means com¬ prising a flexible casing which contains a yieldable sub¬ stance, at a first stage the fixing means being adapted to permit that the patient is oriented in a desired posi¬ tion, partly sunk into the fixing means, and at a second stage the yieldable substance of the fixing means being given a non-yielding state, thereby fixing the patient in the desired position. In radiation treatment as well as in surgical opera¬ tions, the possibility of identifying the target area with great accuracy is highly important. To minimise the risk, the surgeon must be sure of hitting the correct area in the treatment. It is vital that the treatment area can be easily and safely identified on different occasions, since, for example, fractionated radiation treatment requires a num¬ ber of successive treatment sessions. US Patent Specification 5,147,372 discloses a com- puterised tomography unit which comprises a radiation- damping and perforated biopsy arch which is displaceably and pivotally attached to the treatment table on which the patient is placed. By means of the X-ray radiation in CT equipment, a sectional image is obtained in which the biopsy arch is outlined, a suitable hole in the biopsy arch being selectable for introducing a needle point in the target area. Although this prior art unit permits in a simple way the target area to be found, the accuracy is jeopardised by the patient not being fixed to the treat¬ ment table. Besides, the unit is not intended for radia¬ tion treatment. The object of the present invention is to provide a stereotactical instrument with high accuracy when identi¬ fying the target area. A further object of the invention is to provide a stereotactical instrument which permits safe and repeat- able identification of the treatment area. According to the invention, these objects are achieved by means of an instrument as described above, which is characterised by a partially non-radiolucent orienting means which is mounted on at least one longitu¬ dinal side of the frame and which is adapted to indicate the position of the respective image sectional plane through said area in the patient's body, and by the ori¬ enting means comprising a first array of lines of dif¬ ferent lengths. Further developments of the invention are defined in the subclaims. A preferred embodiment of the invention will now be described for the purpose of exemplification, reference being made to the accompanying drawings in which; Fig. 1 is a perspective schematic view of a patient resting in the frame of the instrument; and Fig. 2 illustrates an image sectional plane and its orientation in the stereotactical system of coordinates. The inventive stereotactical instrument, which is generally designated 1 in Fig. 1, comprises an elongate, non-yielding frame 2 which is made of a material that does not cause any artifacts (disturbances) in the im¬ ages, i.e. a material which is translucent to X-rays and other radioactive radiation. A fixing means 3 is adapted to be inserted in the frame 2 which is open at the top and at the ends, said fixing means comprising a flexible casing which is impermeable to fluid and hermetically en- closes a yielding substance, not shown in Fig. 2. On this fixing means, the patient is caused to take the desired position for diagnostics or treatment, the patient par¬ tially sinking into the yieldable fixing means, and a large contact surface against the patient is obtained, see Fig. 2. Subsequently, the fixing means 3 is given a non-yielding state so as to fix the patient in the de¬ sired position. This can be achieved by the casing of the fixing means holding a plurality of small bodies, for ex¬ ample so-called Frigolit beads or the like, which are fixed in their respective positions when a negative pres¬ sure is produced in the impermeable casing. It is also possible to fill the casing with a fluid which can be caused to solidify so as to keep its enforced shape. Thus, the casing can be filled with prepolymerised poly- urethane foam which, when the patient has been oriented in the desired position, is caused to finally polymerise and thus form a non-yielding, fixing compound. By means of a first indicating device 4 fixedly arranged on the frame 2 in the longitudinal direction thereof, and a second indicating device 5 arranged on an arch 6 which is displaceable on the frame in the longitudinal direction thereof, the patient can be oriented in the fixing means for treatment of an area which has previously been located by means of computerised tomography, X-rays etc. The frame 2 is preferably formed with fixing holes (not shown) into which the fixing means can penetrate at its first, yielding stage, and/or fixing lugs 7 penetrat¬ ing into the fixing means so as to fix this at its second, non-yielding stage. Finally, the frame 2 comprises one or more orienting means 8 along each longitudinal side of the frame. The orienting means 8 which preferably is releasably attached to the inside of the frame, consists of a radiolucent support with three arrays of lines preventing radiation, which are made of e.g. wire, strips or thin sections of copper for diagnostic X-ray, angiography, DSA and CT examinations or gas-, liquid- or substance-filled tubes for diagnostic PET and MRI examinations. The first array 10 comprises a number of lines of different lengths ex¬ tending in parallel from one open end of the frame, said lines preferably being parallel also with the bottom of the frame, as shown in Fig. 1. The second array 11 com¬ prises parallel lines extending at an angle to the first array 10 and extending from the first array along each longitudinal side of the frame. The second array 11 is terminated at a third array 12 adjacent the upper edge of the longitudinal side and comprises one or more unbroken lines which preferably are parallel with the lines of the first array. See also Fig. 2 which schematically illus¬ trates a vertical section of the orienting means 8. In this Figure, the frame 2 is indicated by full lines and the upper surface of the fixing means 3 by dashed lines. The frame 2 is supported by a bed unit which allows the patient to be moved, fixed in the frame. The diagnostic equipment produces an image section, for example an MRI or CT sectional image, and the orien- tation of this section is indicated by the orienting means 8. By counting the number of lines in the first array 10, a base value is obtained. The distance between the uppermost unbroken line in the first array and the point in which the image section cuts one of the inclined lines in the second array is measured and yields a sup¬ plementary value, see Fig. 2. Since the distance between the two upper horizontal marks 11 and 12 is known, this distance can be used as a reference for calculating the vertical coordinate in the image sectional plane. Simi- larly, the horizontal coordinate in the image plane can be calculated by the distance between 11 and 12 on the two sides of the frame being known. By means of these values, the orientation of the image section can be de¬ termined with great accuracy. It should be noted that the image section need not be oriented at right angles to the longitudinal axis of the frame 2, but may be oriented at an optional angle, as shown in Fig. 2 in which each point of intersection between the image section and the associ¬ ated line in the second array 11 is positioned on differ¬ ent levels. This Figure schematically illustrates a sec¬ tional image of the patient in which the target area or treatment area 13 appears. In diagnostic use, the ori¬ enting accuracy of the stereotactical system has been about 1 mm, and in repeated treatment using the stereo¬ tactical instrument about 3 mm in the transverse plane and about 6 mm in the longitudinal plane. These values were obtained for target areas close to the diaphragm and were to a certain extent affected by the patient's breathing. In order to reduce the effect of the breathing movements, an abdomen belt (not shown) may be used on such occasions. The stereotactical coordinates are adjusted on the scales 4 and 5 in the treatment room by means of prior- art wall-mounted lasers, mounted and set in conventional manner, which define the system of coordinates for the room/treatment unit. Guided by the values which are ob- tained in the locating of the target point, i.e. the tis¬ sue area to be treated, and which are transferred to the stereotactical instrument, the coordinates are obtained which are necessary to be able to set a radiation source, starting from the frame, such that the beam therefrom is directed to the treatment site or target point. The invention is not restricted to that described above and illustrated in the drawings, but may be modi¬ fied within the scope of the claims.

Claims: CLAIMS 1. Stereotactical instrument for identifying, by means of diagnostic image sectional planes or markers, the spatial position of an area (13) in a patient's body which is to be subjected to treatment, preferably radia¬ tion treatment, the position of the area being previously determined, for example by means of angiogram, PET, DSA, CT, MRI or X-ray equipment, the instrument comprising a non-yielding and radiolucent frame (2) which is arranged to support the patient's body and to support an indicating device (1, 2), a radiolucent fixing means (3) which is arranged inside the frame (2) and on which the patient's body is intended to rest, said fixing means (3) comprising a flexible casing which contains a yieldable substance, at a first stage the fixing means being adapted to permit that the patient is oriented in a de¬ sired position, partly sunk into the fixing means, and at a second stage the yieldable substance of the fixing means being given a non-yielding state, thereby fixing the patient in the desired position, c h a r a c t e r ¬ i s e d by a partially non-radiolucent orienting means (8) which is mounted on at least one longitudinal side of the frame (2) and which is adapted to indicate the posi¬ tion of the respective image sectional plane through said area (13) in the patient's body, and the orienting means (8) comprising a first array (10) of lines of different lengths. 2. Instrument as claimed in claim 1, c h a r a c ¬ t e r i s e d in that the lines of the first array (10) are parallel. 3. Instrument as claimed in claim 1 or 2, c h a r ¬ a c t e r i s e d in that the orienting means (8) com- prises a second array (11) of parallel lines extending at an angle to the first-mentioned lines (10), all lines preventing radiation. 4. Instrument as claimed in claim 3, c h a r a c ¬ t e r i s e d in that the orienting means (8) comprises a third array (12) of one or more unbroken lines at the other end of the angular lines (11), said array (12) being parallel with the first array (10) . 5. Instrument as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that said lines (10-12) are made of copper wire arranged on a radiolucent support (9) . 6. Instrument as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that said lines (10-12) are made of tubes which are filled with gas, liquid or sub¬ stance, for PET and MRI diagnostics. 7. Instrument as claimed in claim 5 or 6, c h a r - a c t e r i s e d in that the orienting means (8) is re- leasably attached to the frame (2) . 8. Instrument as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that scales (4, 5) are applied to the outside of the frame and to the arch for directing the position of the frame in the room of treatment. 9. Instrument as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the frame (2) comprises fixing holes and/or fixing lugs (7) for fixingly engaging the fixing means (3) at its second stage.

Inventors: LAX INGEMAR, LAX, INGEMAR
Applicants: ELEKTA INSTR AB, LAX INGEMAR, ELEKTA INSTRUMENT AB, LAX, INGEMAR
Application year: 1994
Main classification: A61B19
IPC codes: A61B5, A61B19, A61N5